💡 Detailed Explanation
Translation: I play tennis with my friend every Sunday.
- Grammatical point: Time particle に (ni) with specific days of the week.
- Explanation: The particle 'に' is used to mark a specific point in time or a specific day (like 日曜日 - Sunday). While '毎週' (every week) doesn't take 'に', specifying '日曜日' makes the time specific enough to license 'に'.
- Why other choices are incorrect:
- は (wa): Not used to mark time slots in standard descriptive frames like this unless contrasted.
- が (ga): Subject marker.
- を (o): Object marker.